Spectrally sensitized silver halide photographic emulsion

ABSTRACT

A silver halide photographic emulsion containing two kinds of carboxyalkyl-bearing carbocyanine sensitizing dyes is disclosed. The emulsion is spectrally sensitized over a wide green light wavelength range of from 500 - 580 nm and has high sensitivity to green light in flash exposure. Photographic materials produced by using this emulsion are especially useful for information transmitting systems such as a press facsimile.

ilnited States Patent 1 Qhkubo et al. Oct. 30, 1973 [54] SPECTRALLY SENSITIZED SILVER 3,173,791 3/1965 Kalenda 96/124 HALIDE PHOTQGRAPHKC EMULSION 3,364,031 1/1968 Jones et a1 96/124 [73] Assignee: Fuji Photo Film Co., Ltd., Minami Ashigara-shi, Kanagawa, Japan [22] Filed: June 7, 1971 [21] Appl. No.: 150,606

[30] Foreign Application Priority Data June 5, 1970 Japan 45/48546 [52] US. Cl. 96/124, 96/137 [51] Int. Cl G03c 1/14 [58] Field of Search 96/124 [56] References Cited UNITED STATES PATENTS 2,973,264 2/1961 Nys et al 9 6/124 OTHER PUBLICATIONS Defensive Publication, T875,028, 8750.G 7l4 Primary Examiner.l. Travis Brown AttorneySughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT A silver halide photographic emulsion containing two kinds of carboxyalkyl-bearing carbocyanine sensitizing dyes is disclosed. The emulsion is spectrally sensitized over a wide green light wavelength range of from 500 580 nm and has high sensitivity to green light in flash exposure. Photographic materials produced by using this emulsion are especially useful for information transmitting systems such as a press facsimile.

6 Claims, 5 Drawing Figures SPECTRALLY SENSITIZED SILVER HALIDE PHOTOGRAPHIC EMULSION BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a spectrally sensitized silver halide photographic emulsion. More specifically, this invention relates to a silver halide photographic emulsion having a spectral sensitization region at 500 to 580 nm and a high sensitivity to green light in flash exposure. The term flash exposure will be'defined later 2. Description of the Prior Art With the advent of the age of information, various systems for the rapid transmission of information have been developed. They include, for example, a press facsimile system for transmitting a newspaper manu: script rapidly to a remote locality, a high speed photo typesetting system for rapidly setting up a form, and a cathode ray tube display system which, immediately transforms the information produced by an electronic computer into letters or figures. Exposure for a time as short as less than I 100,000th of a second, especially about 1/l,000,000th of a second, is frequently used in the equipment for these rapid information transmitting systems. In recent years, there has been a very brisk demand for photographic materials for use in such systems.

l-ligh illuminance light sources such as a xenon arc lamp or a high pressure mercury lamp in combination with a high speed shutter, or a xenon flash lamp or cathode ray tube are used as light sources in such equipment. As the cathode ray tube, those generally known to be used for flying spot which have a fluorescent substance with a short afterglow time are used. For example, such fluorescent substances which are called P-ll, P45, P-l6, and P-24 are used. It is known that in an emission spectroscopic energy distribution, a peak exists at 460 nm for P-l 1, and at 385 nm for P-l 6. Since such distribution corresponds to the spectral sensitivity region inherent to photosensitive silver halide, spectral sensitizationof a photographic material to be exposed to these fluorescent substances is not particularly necessary. On the other hand, P115" is known to have a peak at 505 nm in its emission spectroscopic energy distribution, and P-24, at 520 nm. Sensitivity to green light need be imparted to photographic materials for recording images on such cathode ray tubes.

The xenon lamp emits light over a relatively wide range of wavelengths. Radiation which has left the light source converges through a condenser lens, a negamatrix, a main lens, a prism, a reflector, or a special lens or prism for letter deformation or other purposes, and forms an image on the light-sensitive surface of a photographic material. Because of the optical system used in the path of these systems, light radiation of shorter wavelengths is absorbed to a greater extent, and the light which reaches the light-sensitive surface contains a reduced proportion of radiation in the range from ultraviolet to blue, and a larger proportion of green light or radiation of longer wavelengths. For this reason, it becomes essential to subject the photographic material to green color sensitization so that its overall sensitivity will be increased.

As previously stated, the afterglow time of the luminescence of a cathode ray tube is asshort as 2 l/10,000,000th of a second to 1/100,000th of a second. The xenon flash lamp used in the above-described information transmitting systems also has an afterglow time much the same as this. The term flash exposure," as used in the present specification, generically refers to such a short time exposure to these light sources.

In the case of the high pressure mercury lamp, bright lines at 546 nm and 577 nm are effectively used. Radiation of shorter wavelengths, 405 nm and 436 nm, are less effective as in the case of the xenon lamp. Three bright lines at 300 nm to 370 nm are hardly utilized. Hence, the spectral sensitization of the silver halide needs to be performed corresponding to the two bright lines'at greater than 500 nm.

It is well known in the art of producing silver halide photographic emulsions that when a sensitizing dye is added to a silver halide emulsion, the sensitive wavelength area of the silverhalide emulsion is broadened, and the emulsion is spectrallysensitized.'One kind, and in many instances two or more kinds, of sensitizing dyes are used for sensitizing the desired spectral sensitization wavelength region of many photographic materi als'. When a combination of sensitizing dyes is used, the resulting sensitivity is often lower than that which would be obtained by using the respective dye alone. For example, when a combination of two or more sensitizing dyes having different spectral sensitization wavelength regions is'used to sensitize the desired spectral sensitization wavelength region, the strong sensitizing ability of the longer wavelength region of a sensitizing dye having a spectral sensitivity maximum in the longer wavelength region (the strong sensitizing ability being caused by an agglomerated mass of the sensitizing dye on silver halide particles) is influenced markedly by the other sensitizing dye. having a spectral sensitivity in a shorter wavelength region. This frequently results in a reduced sensitizing ability in the longer wavelength region.

' One of the big problems in. spectral sensitization techniques is considered to be the discovery of sensitizing dyes which, when used in combination, do not adversely affect each other,and which preferably have an increased spectral sensitivity. However, strict selectiv-. ity is required between two groups of dyes which, when used in combination, increase in sensitizing ability. An apparently slight difference in the chemical structural formula often exerts a marked influence on the strength of the spectral sensitizing action. it is generally thought therefore that the photographic effect of sensitizing dyes is difficult to predict from their chemical structural formulas alone.

The present invention concerns the spectral sensitization by flash exposure. Known methods of increasing spectral sensitivity are generally. based on the results obtained from experiments on the exposure time longer than l/l ,000th of a second. The spectral sensitizing action by flash exposure, however, differs unexpectedly from that of exposure for the previously known duration. This difference is outstanding especially with sensitizing dyes intended for a region of relatively short wavelengths and used for sensitizing the green light region at 500 to 580 nm. This'is considered to be due to the diversity of the oxidizability-reducibility of the absorbed dye itself. Furthermore, the difference is much more marked in the case of strong spectral sensitizing action in a green region.

Accordingly, it was impossible to apply conventional findings simply to'achieving the objectives of the present invention. k

An object of the present invention is to provide a photographic material which is spectrally sensitized over a wide green light wavelength region at 500 to 580 nm and which has a high sensitivity to green light in flash exposure so-that it can be used commonly for information transrnitting' systems using various light sources.

SUMMARY OF THE INVENTION The above objective is achieved by adding to a silver halide photographic emulsion two carboxyalkylcontaining carbocyanine dyes of the following general formulas (I) and (II) whereineach of R R R and R is an alkyl group such as a methyl, an ethyl, an n-propyl, or an n-butyl group, or a substituted alkyl group such as a B-hydroxyethyl, a B-acetoxyethyl, a B-cyanoethyl, a y-methoxypropyl, a -y-carboxypropyl, a 'y-sulfopropyl, a vinyl methyl, or a benzyl group, with the proviso that at least one of R R R and R 'is a carboxyalkyl group such as a carboxymethyl, a B-carboxyethyl, a y-carboxypropyl, a S-carboxybutyl, or a m-carboxypentyl group, each of V and W is a halogen atom such as a fluorine, a chlorine, or a bromine atom, n is 1 or 2, n is 0, 1 or 2, X is an anion, and I is i or 2; and

mama-1 ('1) auxin-H wherein each of R R and R is an alkyl group such as a methyl, an ethyl, or an n-propyl group, or a substituted alkyl group such as a B-hydroxyethyl, a fi-acetoxyethyl, a B-cyanoethyl, a -y-methoxypropyl, a y-car- .boxypropyl, a 'y-sulfopropyl, a vinyl methyl or a benzyl group, with the proviso that at least one of R R and R, is a carboxyalkyl group such as a carboxymethyl, a B-carboxyethyl, a 'y-carboxypropyl, a S-carboxybutyl, or an w-carboxypentyl group, Y is a halogen atom such as a fluorine, a chlorine, or a bromine atom, n" l or 2, X, is an anion, and I, is 1 or 2.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Thespectral sensitization curve obtained when a dye of the formula (I) is added to a silver halide photographic emulsion is shown in FIG. with respect to a dye of the formula lA given later in the specification. It is seen from this curve that a spectral sensitization maximum exists at 565-580 nm,'and the spectral sensitization characteristics to light having a wavelength of less than 555 nm are poor. On the other hand, the spectral sensitization curve obtained when a dye of the formula (11) is added to a silver halide photographic emulsion is shown in FIG. 3 with respect to a dye of the formula A given later'in the specification. FIG. 3 shows that a spectral sensitization maximum exists at 540-560 nm, and the dye hardly is sensitive to light having a wavelength of greater than 565 nm.

The spectral sensitization curve obtainedwhen both of the dyes of the formulas (I) and (II) are added in this order to a silver halide photographic emulsion is shown in FIG. '4 with respect to dyes of the formulas IA and A, which indicates that the emulsion is spectrally sensitized over the range of 500 to 580 nm.

DETAILED, DESCRIPTION OF THE INVENTION As will be illustrated by the Example given hereinafter,'a silver halide photographic emulsion containing a combination of these dyes is t'ully sensitized to green light in flash exposure. In other words, it has been found that the conjoint use of the dyes of the formulas (I) and (II) produces a superior spectral sensitizing effeet on flash exposure.

Conventional sensitizing dyes often cannot be added to photographic emulsions in sufficient concentrations because of their low solubility organic solvents such as ethanol or methanol. However, the sensitizing dyes used in the present invention have good solubility in organic solvents, and therefore are easily purified on synthesis, and form into solutions. Thus, it becomes easy to add the dye solution to a photographic emulsion.

The sensitizing dyes used in the invention are especially useful with a gelatin-silver halide emulsion such as a silver chloride, silver bromide, silver chlorobromide, silver iodobromide, or silver chloroiodobromide emulsion, but are also capable of fully sensitizing photographic emulsions containing water-permeable col-' loids, water-soluble cellulose derivatives, polyvinyl alcohol, or other hydrophilic synthetic or natural resins or polymers instead of gelatin.

The photographic emulsion of the present invention may be prepared by adding the two kinds of dyes to a photographic emulsion in a conventional manner. It is the general practice to add the dyes as a solution in a suitable solvent. The concentrations of the dyes in the emulsion can be varied over a wide range of l to 200 mg per kilogram of the emulsion according to the desired effect.

Additives usually employed in the production of photographic emulsions, such as stabilizers, toning agents, hardening agents, wetting agents, antifoggants, plasticiz'ers, development accelerators, fluorescent bleaching agents, and developing agents for activator development, may also be added to the emulsion using customary techniques.

The emulsion so prepared may be coated conventionally on a suitable support, such as a film of a cellulose derivative, a film of a synthetic resin, glass, or baryta paper.

According to the present invention, there is obtained a photographic material which has a high sensitivity in the orthochromatic spectral region and a sufficiently low sensitivity to red light, and in which the sensitizing dyes are readily bleached by processing including development, fixation, and rinsing or a processing including activator development and stabilization and remain colorless after the processing. Such photographic materials are especially suitable for use in the rapid information processing described above.

Several examples of the dyes of the formulas (I) and (II) used in the invention are given below. It should be noted however, that these specific examples are not intended in any way to be limiting.

C IE:

I N I l 01 I CH=CHCH 01 f 01 t N/ (2,115 rdmomcmooon, (IA) $215: I aHs N N CH=CHCH Br 01 N N 1115 rtlmcmcmcoon,

(1B) (I /2H5 |3ZH5 N N o1 CH=CHCH Br G1 \I? N/ CHaCHzCI-IzSO'a tinicnzcmooon,

(IQ) c mcmon omcmon N N CH=CH-CH N I- dmcmcmcoo CHQCHQCHiCOOH, (ID) CHQ HCQCHI ZFQ Wm -CH=CHCH= C1 I CHzCHgCHiCOO 2115 U (IIB) (IIE) The sensitizing dyes expressed by the formulas (I) and (11) used in the invention can be synthesized easily by those skilled in the art by known methods. Typical examples of the synthesis of the sensitizing dyes used in the invention will be given briefly below.

SYNTHESIS EXAMPLE 1 Dye of Formula lA Five grams of Z-(B-anilide vinyl)-5,6-dichloro-l,3- diethylbenz-imidazolium iodide and 10 cc of nitrobenzene were reacted by heating in 3 cc of acetic anhydride for 5 minutes; To the resulting solution were added 3.7 g of 3-('y-carboxypropyl)-5'-chloro-1-ethyl-2- methylbenzolium bromide and 3 cc of triethylamine, and the mixture was reacted for 10 minutes by heating 1 under reflux. After completion of the reaction, ether was added to form a precipitate. The precipitate was washed with water, and crystallized with ethanol. The crystals obtained were recrystallized from ethanol to yield a dye having a melting point of 262C in an amount of 1.1 g. The dye had a spectral absorption maximum at 513.5 nm (in methanol).

SYNTHESIS EXAMPLE 2 Dye of Formula lIA Five grams of Z-(B-acetoanilide vinyl)-3-ethyl-naphtho[1,2-d]oxazolium iodide, 5 g of 3-(B-carboxyethyl)- 5 ,6-dichloro-1 -ethyl-Z-methyI-benzimidazolium bromide, and 4 ml of triethylamine were reacted in ml of ethanol by heating for one hour. After completion of the reaction, the reaction solvent was concentrated, and the crystals precipitated were recovered by filtration. The crystals obtained were recrystallized from methanol to yield a dye having a melting point of 214C in an amount of 2.4 g. The dye had a spectral absorption maximum at 505 nm (in methanol).

The invention will be further described by reference to the following Example which is not intended in any way to limit the scope of the invention.

EXAMPLE Four photographic emulsions were prepared each weighing 100 g and containing a silver halide composed of 29 mole percent silver chloride, 70 mole percent silver bromide and 1 mole percent silver iodide (each emulsion containing 45 milligram equivalents of silver and 12 g of gelatin). Four samples were prepared by adding the dyes of the formulas (IA) and (HA) in the amounts indicated below:

Sample Dye (IA) (Dye (HA) 2 0.016 milligram equivalent I 3 0.0l2 milligram equivalent 4 0.008 milligram 0.008 milligram equivalent equivalent Each of'the dyes was added as a solution in methanol. Saponin (0.06 g), as a wetting agent, and 0.27 g of formaldehyde, as a hardener, further were added, and the resulting coating solution was coated on baryta paper (the amount of silver coated, 1.4 milligram equivalents/dm).

The photographic materials so obtained were each exposed for l/ 100th of a second and l/ 1,000,000 of a second respectively through a V--Y 50 color glass fil ter (Tokyo Shibaura Electric Co., Ltd.) and an optical wedge using a Mark'VlI sensitometer (EG & G Company, U.S.A.). As shown in FIG. 5, the above-described color glass filter absorbs light corresponding to the sensitivity region inherent to silver halide, and allows transmission of light corresponding to a spectral sensitization region of about 500 nm or more.

Each of the exposed samples was developed for 2 minutes at C in a developing solution of the following formulation.

N-Methyl para-Aminophenol 2 g Anhydrous Sodium Bisulfite g 'Hydroquinone 7 g Sodium Carbonate Monohydrate 53 g Potassium Bromide 1.5 g

Water to make 1 liter The developed samples were fixed, rinsed, and dried by a usual method.

The same emulsion-coated samples were exposed for l/SO second with a spectral sensitometer (product of Narumi Shokai Co., Ltd.), and subjected to the same processing including development and fixation.

The spectral sensitivity curve of each sample is shown respectively in FIGS. 1, 2, 3 or 4, from which it is noted that the conjoint use of the dyes IA and IIA produced good effects. Green light sensitometry using a sensitometer of the EG & G Company gave the following results.

Relative Sensitivity Relative Sensitivity to green to green light in exposure for light in exposure for Samples lIlQOth of a second i] l,000,000th a second I Not Sensitive Not Sensitive 2 210 The sensitivity values were measured as follows: The reflection density of the resulting image was measured, and the reciprocal of the ratio of the amount of light which gave a density of 0.5 was employed as the sensitivity value. Since the absolute amount-of light through a filter was not measured, the sensitivity values are relative ones. But in the above table, the sensitivities for a given exposure time could be compared The results shown above demonstrate that the Dyes IA and HA in combination have sufficient sensitivity even in flash exposure 8 What is claimed is: I. A silver halide photographic emulsion containing a sensitizing dye of the formula (I) below wherein each of R R R and R. is selected from the group consisting of an alkyl group and a substituted alkyl group, said substituents being selected from the group consisting of a hydroxy group, an acetoxy group, a cyano group, a carboxy group, a sulfo group, a vinyl group, and an aryl group, at least one of R,, R R and R being a carboxyalkyl group, V and W are a halogen atom, n is l or 2, n is 0, l or 2, X is an anion, and l is 1 or 2; and a sensitizing dye of the formula (ll) below:

wherein each of R R and R is selected from the group consisting of an alkyl group and a substituted alkyl group, said substituents being selected from the group consisting of a hydroxy group, an acetoxy group, a cyano group, a carboxy group, a sulfo group, a vinyl group, and an aryl group, at least one of R R and R being a carboxyalkyl group, Y is a halogen atom, n" is l or 2, X is an anion, and I is 1 or 2.

2. The silver halide photographic emulsion according to claim 1, wherein the sensitizing dye of formula (I) is a compound represented by the following formula:

Pi -Z 1 2135 1 2 5 N N c1 C H=C H- C H: 01 Cl N N 1 HgCI-IzCHzC 0 0H 3. The silver halide photographic emulsion according to claim 1, wherein the sensitizing dye of formula (ll) is a compound represented in the following formula 4. The silver halide photographic emulsion according to claim 1, wherein said emulsion is selected from the group consisting of a silver chloride, a silver bromide, a silver chlorobromide, a silver iodobromide, and a silver chloroiodobromide emulsion.

5. The silver halide photographic emulsion according H, to claim 4, wherein said sensitizing dye of the formula l; 0 (l) and wherein said sensitizing dye of the formula (ll) (:1 are present at a level of from 1 to 200 mg per kilogram CH=CHCH of the emulsion. 5 01 6. The silver halide photographic emulsion according to claim 1, wherein said sensitizing dye of the formula CH, CH,O00 CzHs l (l) is selected from the group consisting of 2 5 1 2E115 JHzCHQCOO- Ha U (llH CHzOH I (fHzCHaOI-I N t lHzcoon-(llam) l -CH=CHCH= C1 C1 N T and mcmcmcoofi cmcmcmcoon 40 V d $Hz=CH=CHz im-on cn, EH, j Br %CH=CHCH\ CHCH-CH F B N N Cl r v v 7/ (microscoall; I

C HQCOOH X- 01115 and wherein said sensitizing dye of the formula (II) is wherein X is Cl, Br, or I. selected from the group consisting of v 

2. The silver halide photographic emulsion according to claim 1, wherein the sensitizing dye of formula (I) is a compound represented by the following formula:
 3. The silver halide photographic emulsion according to claim 1, wherein the sensitizing dye of formula (II) is a compound represented in the following formula
 4. The silver halide photographic emulsion according to claim 1, wherein said emulsion is selected from the group consisting of a silver chloride, a silver bromide, a silver chlorobromide, a silver iodobromide, and a silver chloroiodobromide emulsion.
 5. The silver halide photographic emulsion according to claim 4, wherein said sensitizing dye of the formula (I) and wherein said sensitizing dye of the formula (II) are present at a level of from 1 to 200 mg per kilogram of the emulsion.
 6. The silver halide photographic emulsion according to claim 1, wherein said sensitizing dye of the formula (I) is selected from the group consisting of 